1. Field of the Invention
The present invention relates to a draw out apparatus for an air circuit breaker, and more particularly, to a draw out apparatus for an air circuit breaker capable of allowing a circuit breaker body to be stopped at a preset position, by executing idling when an abnormal operation such as an over-draw in operation and an over-draw out operation occurs at the preset position such as a disconnect position, a test position or a connect position, and capable of preventing damage of a circuit breaker and a cradle.
2. Background of the Invention
Generally, an air circuit breaker, a kind of circuit breaker capable of switching a load on an electric circuit, a power line, a substation line, etc., or capable of interrupting a current when an accident such as a ground fault or a short circuit occurs. The air circuit breaker is mainly used for a low pressure device.
The air circuit breaker may be provided with a cradle, for inspection or replacement of a circuit breaker body. The air circuit breaker may be categorized into a fixed type where a circuit breaker body is fixed to a cradle, and a draw-out type where a circuit breaker body is drawn-in or drawn-out of a cradle. Hereinafter, the draw-out type circuit breaker will be explained.
For current conduction, the circuit breaker body is inserted into the cradle. In such an inserted state, the circuit breaker executes a closing operation (ON) and a trip operation (OFF). In a closed state of the circuit breaker (ON), when an accident current occurs from a line, the circuit breaker interrupts a current after a predetermined time lapses or immediately according to a size of the accident current.
Among apparatuses applied to the air circuit breaker, a draw out apparatus serves to insert a circuit breaker body into a cradle or to draw the circuit breaker body out of the cradle. Generally, the draw out apparatus for the air circuit breaker includes a moving rack having thereon a circuit breaker body and linearly-moveable into a cradle; and a screw shaft (or a lead screw) screw-connected to the moving rack and configured to transfer a rotational driving force provided from a handle to the moving rack after converting the rotational driving force into a linear driving force. Once the handle is connected to the screw shaft to thus be rotated, a rotational driving force is converted into a linear driving force by the screw shaft. Accordingly, the moving rack is linearly moved, and thus the circuit breaker body disposed on the moving rack is inserted into or drawn out of the cradle.
FIG. 1 is a view illustrating an inner structure of an air circuit breaker in accordance with the conventional art. FIG. 2 is a planar view of a draw out apparatus for an air circuit breaker in accordance with the conventional art. And FIG. 3 is a perspective view of a screw shaft and a coupling applied to a draw out apparatus for an air circuit breaker in accordance with the conventional art.
The conventional air circuit breaker 100 includes a circuit breaker body 101 having movable contactors for phases, fixed contactors for phases, and having an insulation partition wall for electrically insulating the movable contactors and the fixed contactors from each other; a cradle 102 configured to accommodate therein the circuit breaker body, and having a terminal part at a rear side thereof, the terminal part to which a power side line and a load side line of an external power system are connected; a switching mechanism 103 configured to provide a driving force to simultaneously open and close the movable contactors (not shown) inside the circuit breaker body 101; and a girder 104 installed at a lower end of a front surface of the cradle 102, and configured to provide a user with an access means for manipulation of the air circuit breaker.
As shown in FIG. 2 or FIG. 3, the conventional draw out apparatus for the air circuit breaker includes a draw out shaft 122, a screw shaft 121, a moving rack 120, a coupling 126, springs 127, 128, a reset operator 124, an indicating rod 123, and a lock plate 129. The coupling 126 and the springs 127, 128 are moveable to a power transmission position where a driving force generated from the handle (H) to draw in or draw out the circuit breaker body is transferable to the moving rack 120, and a power transmission stop position where power transmission is not executable.
When pressed by a user, the reset operator 124 pressurizes the springs 127, 128 such that the springs store an elastic energy therein. As a result, the coupling 126 is disposed at a position where a rotational force of the draw out shaft 122 is transferable to the screw shaft 121. The reset operator 124 includes a fore end part 124b extending by penetrating a supporting member 125 and configured to restrict a downward movement of the reset operator 124, a reset pressing end part 124a, and a protrusion (not shown) at one side thereof. A latch groove 124c, configured to insert a latch part 123b of the indicating rod 123 thereinto for a restricted state or to separate the latch part 123b therefrom for a released state, is provided at the protrusion.
The indicating rod 123 (or an indicator) is provided with the latch part 123b configured to restrict the reset operator 124, or configured to release a restricted state of the reset operator 124 when the circuit breaker body 101 is at a connect position, a test position or a disconnect position. And the indicator rod 123 is provided with a twisted part 123a connected to the moving rack 120, and is rotated as the moving rack 120 is linearly moved to thus indicate a position of the circuit breaker body 101.
A position display part 123c of the indicating rod 123 has arrows displayed on a sectional surface thereof in correspondence to three positions of the circuit breaker body 101, i.e., a connect position, a test position, and an disconnect position. And marks corresponding to the connect position, the test position, and the disconnect position are displayed around a position display part expositing hole 104c of the girder 104.
The lock plate 129 may restrict the coupling 126 by contacting an outer circumferential surface of the coupling 126. And the lock plate 129 temporarily restricts the coupling 126 whenever the indicating rod 123 releases the reset operator 124 on the three positions, thereby temporarily stopping a draw in operation or a draw out operation of the circuit breaker body. More specifically, the lock plate 129, a plate member, is provided with an angular inner circumferential part 129a such that a rotation of the coupling 126 is stopped when an angular outer circumferential part 126b of the coupling 126 is inserted in the angular inner circumferential part 129a. Whenever the latch part 123b of the indicating rod 123 releases the reset operator 124 on three positions of the circuit breaker body 10 (i.e., a connect position, a test position, and an disconnect position), the lock plate 129 downward moves (refer to FIG. 2) by a restoration force of an upper spring 127, i.e., a tensile force of the upper spring 127. As a result, as shown in FIG. 6, as the angular outer circumferential part 126b of the coupling 126 is inserted into the angular inner circumferential part 129a, a rotation of the coupling 126 is temporarily stopped.
An operation of the conventional draw out apparatus for an air circuit breaker will be explained.
FIGS. 4 to 6 are views illustrating an operation state of the draw out apparatus for an air circuit breaker in accordance with the conventional art, which illustrate a power transmission stopped state, a power transmission enabled state, and a power transmission restricted state by the coupling, respectively.
Referring to FIG. 4, the coupling 126 is positioned at a power transmission stopped state where the screw shaft 121 and the draw in and output shaft 122 are not connected to each other. The springs 127, 128 are in a discharged state of an elastic energy, and the reset operator 124 is on a downward-moved position.
In this state, even if the handle (H) is rotated by being connected to a handle connection part 122a of the draw out shaft 122, the draw out shaft 122 performs only idling without transmitting a rotational force to the screw shaft 121. The reason is because the draw out shaft 122 is not connected to the screw shaft 121, but is merely in a contacted state with the end of the screw shaft 121. Once the circuit breaker body reaches one of three positions (a disconnect position, a test position or a connect position), the draw out apparatus for an air circuit breaker automatically returns to the initial state.
In this case, as a user presses the reset pressing end part 124a of the reset operator 124, the upper spring 127 is compressed by a spring supporting part (not shown) of the reset operator 124 which upward moves linearly as shown in FIG. 5. As a result, the upper spring 127 stores an elastic energy therein, so the coupling 126 is pressurized to be moved upward. As an angular inner circumferential surface part 126b-1 of the coupling 126 is connected to a rectangular part 121b of the screw shaft 121 and a rectangular part 122c of the draw out shaft 122, the screw shaft 121 and the draw out shaft 122 are connected to each other. As a result, the circuit breaker body is ready to be drawn in the cradle or drawn out of the cradle.
Referring to FIG. 5, in a state where power transmission is enabled as the screw shaft 121 and the draw out shaft 122 are completely connected to each other, a user may connect the handle (H) to the handle connection part 122a of the draw out shaft 122, and rotates the handle (H) in a counterclockwise direction (a clockwise direction) in order to draw in (draw out) the circuit breaker body 101. As a result, the draw out shaft 122 is rotated in a counterclockwise direction (a clockwise direction), so the screw shaft 121 connected to the draw out shaft 122 by the coupling 126 is rotated in a counterclockwise direction (a clockwise direction). Accordingly, the moving rack 120 moves upward (downward) along a screw part 121a of the screw shaft 121 which rotates in a counterclockwise direction (a clockwise direction). As the moving rack 120 moves upward (downward), the circuit breaker body 101 moves in a draw in (draw out) direction.
Once the circuit breaker body 101 reaches one of a connect position, a test position and a disconnect position by being moved in a draw in direction or a draw out direction, the twisted part 123a of the indicating rod 123 is rotated as the moving rack 120 moves. As a result, the latch part 123b of the indicating rod 123 is separated from the latch groove 124c of the reset operator 124, so the reset operator 124 is released. Accordingly, as shown in FIG. 6, the lock plate is downward moved by the springs 127, 128 which are restored with discharging an elastic energy. As a result, the angular inner circumferential part 129a of the lock plate 129 is engaged with the angular outer circumferential part 126b of the coupling 126, thereby restricting the coupling 126. Accordingly, as the screw shaft 121 and the draw out shaft 122 are temporarily stopped, a user may be notified that the circuit breaker body has reached one of a connect position, a test position and a disconnect position.
Referring to FIG. 6, if the user stops the handle (H) being rotated, the coupling 126 is backward moved by an elastic force of the upper spring 127 which is extended. As a result, the draw out apparatus for an air circuit breaker returns to the initial state shown in FIG. 4. Here, the reset operator 124 returns up to a position where the fore end part 124b is locked by the supporting member 125. Further, as the coupling 126 is backward moved, a circular outer circumferential part 126a of the coupling 126 is positioned within the angular inner circumferential part 129a of the lock plate 129. The coupling 126 is in a released state where the coupling 126 is freely rotatable. Further, the angular inner circumferential surface part 126b-1 of the coupling 126 is engaged with only the rectangular part 122c of the draw out shaft 122, and the rectangular part 121b of the screw shaft 121 is released. As a result, even if the handle is connected to the draw out shaft 122 to thus be rotated, the draw out shaft 122 executes idling. This may protect the components of the draw out apparatus for an air circuit breaker, from damage due to an excessive over-rotation.
In the conventional draw out apparatus for an air circuit breaker, whenever the circuit breaker body reaches a connect position, a test position and a disconnect position, the reset operator is released and the coupling moves to a driving transmission stopped position by the spring. This may cause the draw out shaft and the screw shaft to be disconnected from each other. As a result, even if a user excessively rotates the handle, power transmission is not executed. This may prevent an over-driving of the components of the draw out apparatus for an air circuit breaker, and damage thereof.
However, in the conventional draw out apparatus for an air circuit breaker, a user may press the reset operator on a connect position or a disconnect position for a driving connection state shown in FIG. 5. Then, the user may operate the handle in a closing direction in an already connected (closed) state, or may operate the handle in an opening direction in an already disconnected (open) state. This may cause an over-driving of the components of the draw out apparatus for an air circuit breaker, resulting in damage of the components.